This invention relates to spread-spectrum communications, and more particularly to code-division-multiple-access (CDMA) cellular, packet-switched systems.
Presently proposed for a standard is a random-access burst structure which has a preamble followed by a data portion. The preamble has 16 symbols, the preamble sequence, spread by an orthogonal Gold code. A mobile station acquires chip and frame synchronization.
A general object of the invention is an efficient method for packet data transfer on CDMA systems.
Another object of the invention is high data throughput and low delay.
According to the present invention, as embodied and broadly described herein, an improvement to a code-division-multiple-access (CDMA) system employing spread-spectrum modulation, is provided. The CDMA system has a base station (BS) and a plurality of remote stations. The base station has BS-spread-spectrum transmitter and a BS-spread-spectrum receiver. Each of the plurality of remote stations has an RS-spread-spectrum transmitter and an RS-spread-spectrum receiver. The method comprises the steps of transmitting from BS-spread-spectrum transmitter, a broadcast common-synchronization channel. The broadcast common-synchronization channel has a common chip-sequence signal common to the plurality of remote stations. Further, the broadcast common-synchronization channel has a frame-timing signal.
A first RS-spread-spectrum receiver, located at a first remote station, the method includes the step of receiving the broadcast common-synchronization channel. From the received broadcast common-synchronization channel, the steps include determining frame timing at the first RS-spread-spectrum receiver from the frame-timing signal.
At a first RS-spread-spectrum transmitter, located at the first remote station, the steps include transmitting an access-burst signal. The access-burst signal has a plurality of segments. A segment is an interval in time of the access-burst signal. Each segment has a preamble followed by a pilot signal. The plurality of segments preferably also has a plurality of power levels, respectively. Preferably, the plurality of power levels increase sequentially, with each segment.
At the BS spread-spectrum receiver the steps include receiving the access-burst signal at a detected-power level. In response to receiving the access-burst signal, from the BS-spread-spectrum transmitter, the steps include transmitting to the first RS-spread-spectrum receiver an acknowledgment signal.
At the first RS-spread-spectrum receiver the steps include receiving the acknowledgment signal. In response to receiving the acknowledgment signal, the steps include transmitting from the first RS-spread-spectrum transmitter, to said BS-spread-spectrum receiver, a spread-spectrum signal having data.
Additional objects and advantages of the invention are set forth in part in the description which follows, and in part are obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention also may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.